Method for processing vegetable oils

ABSTRACT

The present invention provides certain improvements in methods for processing vegetable oils and apparatus for carrying out such methods. One embodiment provides a method for processing a partially processed oil including glycerides and a volatilizable impurity fraction. The partially processed oil may processed by driving off a first volatiles stream comprising a portion of the glycerides and at least a portion of the volatilizable impurity fraction, leaving a deodorized oil. The first volatiles stream may be introduced into a first condensing chamber and a glyceride-rich, impurity-poor first condensate may be condensed from the first volatiles stream, leaving a glyceride-poor, impurity-rich second volatiles stream. The second volatiles stream may be passed into a second condensing chamber and a glyceride-poor, impurity-rich second condensate may be condensed from the second volatiles stream.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/484,797, filed Jun. 2, 2004, which is a U.S. National Phaseapplication of International Application No. PCT/US2001/051220, filedNov. 13, 2001, which claims priority to U.S. Provisional Application No.60/307,577, filed Jul. 23, 2001, the disclosures of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to methods and apparatus for processingvegetable oils and animal fats such as lard, tallow, and fish oil. Theinvention may be used to increase yield in oil processing by recoveringdesirable components from a volatile stream exiting an oil deodorizer.

BACKGROUND

The primary components of most vegetable oils are triglycerides.Depending on the oil source, these triglycerides may include a varietyof saturated, partially saturated, and unsaturated fatty acids (e.g.,oleic, linoleic, linolenic, lauric, palmitic, and myristic acids)esterified on a glycerol molecule in various combinations. Raw,unprocessed vegetable oils often contain varying amounts of othercompounds, too. Some of these compounds are desirable components of theoil, i.e., they need not be removed during processing to yield acommercially salable oil. Such desirable components commonly includediglycerides, tocopherols, sterols, and sterol esters, and some oilswill include other desirable components (e.g., tocotrienols in palmoil). Other compounds in the raw vegetable oil are undesirableimpurities which can adversely affect the taste, smell, appearance, orstorage stability of a refined oil and hence are beneficially removed.These undesirable impurities generally include phosphatides, free fattyacids, odiferous volatiles, colorants, waxes, and various metalcompounds. Some of these undesirable impurities (e.g., metal compounds)are contaminants which have little or no commercial value. Free fattyacids and some other components of raw oils are undesirable in aprocessed oil and may be considered “undesirable impurities” in thatcontext, but may still have meaningful commercial value.

Vegetable oil impurities are typically removed in three separate steps,particularly degumming and/or alkali refining, bleaching, and physicalrefining and/or deodorizing. For certain oils, it may be desirable to“degum” the raw oil prior to alkali refining. Degumming and alkalirefining generally remove phosphatides, soaps, and other impurities suchas metals. Bleaching may improve the color and flavor of refined oil bydecomposing peroxides and removing oxidation products, tracephosphatides, and trace soaps. In the final physical refining and/ordeodorizing step, remaining volatilizable impurities are removed toyield a deodorized vegetable oil having the desired finalcharacteristics. The volatilizable impurities removed in thedeodorization process commonly include free fatty acids, aldehydes,ketones, alcohols, and other hydrocarbon impurities. Some of theseimpurities may come directly from the oil seeds themselves while othersmay arise from pesticides, fungicides, and other compounds applied tothe seeds or to the plants from which the seeds are derived.

Most physical refining and deodorization processes rely on volatilitydifferences to drive off the relatively more volatile impurities fromthe relatively less volatile desirable components of the vegetable oil.Unfortunately, some of the desirable components of the vegetable oil maybe driven off with the volatilizable impurities during the deodorizationprocess. As a consequence, the volatiles stream exiting the deodorizerwill include a substantial fraction, if not substantially all, of theimpurities, but may also include a varying amount of desirable compoundssuch as triglycerides, diglycerides, tocopherols, sterols, sterolesters, and tocotrienols. Since these desirable compounds could remainin the final deodorized vegetable oil without objection, the volume ofsuch desirable compounds in the vapor stream exiting the deodorizerrepresents loss of a commercially valuable product.

Most conventional deodorizing processes are carried out usingvacuum-steam deodorization, in which a heated vegetable oil is contactedwith steam at a low operating pressure. The volatilizable impurities andsome of the desirable vegetable oil components are carried off with thesteam. This steam-laden vapor stream is subsequently condensed into animpurity-laden liquid, with some or all of the steam being vented to theatmosphere through the vacuum system. Other deodorizing processes mayemploy heated nitrogen or other gases instead of steam, but suchprocesses are less widely used in vegetable oil processing.

Because of the relatively high concentration of impurities, thecondensate from the deodorizer vapor stream has limited commercialvalue. While it is theoretically possible to reintroduce this condensateinto the raw oil feed, this is often ill-advised because it canunacceptably degrade the quality of the starting oil and overburden thecapacity of the deodorizer. It may be possible to resell the condensatefor further processing to use as an animal feed additive or the like,but the value of such a condensate is significantly less than the valueof the deodorized vegetable oil.

SUMMARY OF THE INVENTION

The present invention provides certain improvements in methods forprocessing vegetable oils and apparatus for carrying out such methods.In accordance with one embodiment, the invention provides a method forprocessing a partially processed oil which includes glycerides and avolatilizable impurity fraction. In accordance with this method, thepartially processed oil is deodorized by driving off a first volatilesstream comprising a portion of the glycerides and at least a portion ofthe volatilizable impurity fraction, leaving a deodorized oil. The firstvolatiles stream may be introduced into a first condensing chamber and aglyceride-rich, impurity-poor first condensate may be condensed from thefirst volatiles stream, leaving a glyceride-poor, impurity-rich secondvolatiles stream. The second volatiles stream may be passed into asecond condensing chamber and a glyceride-poor, impurity-rich secondcondensate may be condensed from the second volatiles stream. If thepartially processed oil of this embodiment includes tocopherols and/ortocotrienols, the first volatiles stream may include a portion of thetocopherols and/or tocotrienols and a majority of the tocopherols and/ortocotrienols in the first volatiles stream may be condensed in the firstcondensate.

A method of processing vegetable oil in accordance with anotherembodiment of the invention comprises refining the vegetable oil toyield a refined vegetable oil. The refined vegetable oil is bleached toyield a bleached vegetable oil comprising glycerides and a volatilizableimpurity fraction. The bleached vegetable oil is deodorized to yield adeodorized vegetable oil and a first volatiles stream. The firstvolatiles stream comprises a portion of the glycerides and a majority ofthe volatilizable impurity fraction of the bleached vegetable oil. Thefirst volatiles stream is partially condensed to yield a glyceride-richfirst condensate and a glyceride-poor second volatiles stream. Thesecond volatiles stream may comprise a majority of the volatilizableimpurity fraction. In one particular embodiment, the first volatilesstream is partially condensed by cooling the first volatiles stream.This cooling may be accomplished by spraying a portion of theglyceride-rich first condensate back into the volatiles stream.

Another embodiment of the invention provides a method for processing avapor stream from a vegetable oil deodorizer, the vapor streamcomprising desirable glycerides and undesirable impurities. The vaporstream is partially cooled to preferentially condense a glyceride-richrecovered oil, yielding an impurity-rich byproduct vapor. In oneembodiment of this method, the vapor stream is cooled by spraying therecovered oil in the vapor stream or otherwise contacting the vaporstream with the recovered oil.

In yet another embodiment, the invention provides a method forprocessing a vegetable oil comprising desirable compounds andvolatilizable impurities. In accordance with this method, the vegetableoil is introduced into a deodorizer maintained at a pressure of nogreater than 10 mm Hg. The vegetable oil is contacted with steam in thedeodorizer to volatilize a substantial fraction of the impurities and aminor fraction of the desirable compounds into a volatiles stream,leaving a deodorized vegetable oil. The volatiles stream is passed intoa recovery condenser maintained at a pressure of no greater than 10 mmHg. The volatiles stream is partially cooled to selectively condense asubstantial fraction of the desirable compounds into a recovered fluid,leaving a byproduct stream comprising a substantial fraction of theimpurities in the volatiles stream. A portion of the recovered fluid maybe sprayed back into the volatiles stream to cool the volatiles stream.The byproduct stream may be passed into a byproduct condenser maintainedat a pressure of less than 10 mm Hg and the byproduct stream may befurther cooled to condense a majority of the remaining impurities into abyproduct fluid.

An alternative embodiment of the invention provides a vegetable oilprocessing system which includes a deodorizer maintained at an elevatedtemperature and a pressure of no greater than 10 mm Hg. The deodorizermay include a first vapor outlet through which volatilized impuritiesand a desirable glyceride fraction may exit. A recovery condenser has afirst vapor inlet in fluid communication with the first vapor outlet; acondensing chamber maintained at a pressure no greater than 10 mm Hg; asecond vapor outlet through which a glyceride-poor byproduct vaporstream may exit the condensing chamber; and a recovered fluid outletthrough which a glyceride-rich recovered fluid may exit the condensingchamber. A recovered fluid spray system is in fluid communication withthe recovered fluid outlet. The recovered fluid spray system may includea recovery spray head in fluid communication with the condensing chamberand a recirculation pump adapted to deliver a cooling flow of therecovered fluid to the recovery spray head. A byproduct condenser has asecond vapor inlet and a byproduct condensing chamber maintained at apressure no greater than 10 mm Hg. The second vapor inlet is in fluidcommunication with the second vapor outlet and receives the byproductvapor stream. The byproduct condensing chamber may be adapted tocondense a substantial fraction of the impurities in the byproduct vaporstream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram schematically illustrating aspects of avegetable oil processing system in accordance with one embodiment of theinvention.

FIG. 2 is a more detailed schematic view of portions of the oilprocessing system shown in FIG. 1 in accordance with a furtherembodiment of the invention.

FIG. 3 is a more detailed schematic view of portions of the oilprocessing system shown in FIG. 1 in accordance with an alternativeembodiment of the invention.

DETAILED DESCRIPTION

Various embodiments of the present invention provide methods andapparatus for processing oils, e.g., vegetable oils. The followingdescription provides specific details of certain embodiments of theinvention illustrated in the drawings to provide a thoroughunderstanding of those embodiments. It should be recognized, however,that the present invention can be reflected in additional embodimentsand the invention may be practiced without some of the details in thefollowing description.

FIG. 1 provides a schematic overview of a vegetable oil processingsystem in accordance with one embodiment of the invention. In thissystem, a raw oil may be delivered from a raw oil supply 10 to anoptional degumming subsystem 12 via a raw oil feed line 11. A widevariety of raw oils may be used, including those derived from soybeanoil, corn oil, cottonseed oil, palm oil, peanut oil, rapeseed oil,safflower oil, sunflower seed oil, sesame seed oil, rice bran oil,coconut oil, canola oil, and mixtures thereof. While the presentinvention may be used beneficially with virtually any vegetable oil, ithas particular utility in processing vegetable oils with relatively highlosses in the deodorization and/or physical refining process (e.g., palmoil and coconut oil), and oils with more valuable substances such astocopherols, tocotrienols, or sterols. Embodiments of the invention mayalso be used in processing animal fats such as lard, tallow, and fishoil.

The raw oil may be degummed, if necessary, in the degumming/alkalirefining subsystem 12. Degumming generally refers to the process ofremoving phosphatides from crude vegetable oils. Any of a variety ofdegumming processes known in the art may be used. One such process(known as “water degumming”) includes mixing water with the vegetableoil and separating the resulting mixture into an oil component and anoil-insoluble hydrated phosphatides component, sometimes referred to as“wet gum” or “wet lecithin.” Such processes are generally known in theart and are also outlined in U.S. Pat. No. 6,172,248, the entirety ofwhich is incorporated herein by reference. Such a process is commonlyfollowed by alkali refining, as explained below. In an alternativeembodiment more useful in connection with physical (as opposed toalkali) refining, phosphatide content is further reduced by otherdegumming processes, such as enzymatic degumming (e.g., ENZYMAX fromLurgi), chemical degumming (e.g., SUPER/UNI degumming from Unilever, TOPdegumming from VandeMoorrtele/Dijkstra CS, or SOFT degumming fromTirtiaux).

If so desired, raw or degummed oil may be refined via alkali refining inthe degumming/alkali refining subsystem 12 prior to bleaching the oil.Generally, vegetable oil refining involves removing free fatty acids andphosphatides from the vegetable oil. Most refining operations employeither alkali refining or physical refining, also referred to as steamrefining. In alkali refining, the most common of the two refiningmethods, the vegetable oil is commonly mixed with a hot, aqueous alkalisolution, producing a mixture of refined oil, also known as “neutraloil,” and soapstock. The soapstock is then separated from the refinedoil.

The refined oil from the degumming/alkali refining subsystem 12 may bedelivered to the bleaching subsystem 14 via a refined oil feed line 13.Alternatively, raw oil may be delivered directly from the raw oil supply10 to the bleaching system without any pre-treatment in thedegumming/alkali refining subsystem 12. The nature and operation of thebleaching subsystem 14 will depend, at least in part, on the nature andquality of the oil being bleached. Generally, the raw or refined oilwill be mixed with a bleaching agent which may combine with oxidationproducts, trace phosphatides, trace soaps, and other compounds adverselyaffecting the color and flavor of the oil. As is known in the art, thenature of the bleaching agent can be selected to match the nature of therefined oil to yield a desirable bleached oil. Bleaching agentsgenerally include natural or “activated” bleaching clays, also referredto as “bleaching earth,” activated carbon, and various silicates.Suitable bleaching earths are commercially available and U.S. Pat. No.6,027,755, the entirety of which is incorporated herein by reference,discloses properties of one useful bleaching earth product.

The resultant bleached oil is delivered from the bleaching subsystem 14to the physical refiner/deodorizer 20 through a bleached oil feed line15. If the oil has been alkali refined, the refined, bleached oil may bedeodorized in the physical refiner/deodorizer 20. Physical refining is asteam distillation process similar to that used in conventionalvegetable oil deodorizing. Such deodorizing processes are explained inmore detail below in connection with the deodorizer 20, but it should beunderstood that this same process and equipment may be used tophysically refine the oil. Such a physical refining or deodorizingprocess may include contacting the vegetable oil with steam to vaporizeand carry away free fatty acids and other impurities. For example, thevapor stream exiting a physical refining unit of the refining subsystem12 may be passed to a recovery condenser 40 and byproduct condenser 70as discussed below in connection with the deodorizer 20. FIG. 1 showsthe deodorizer 20, recovery condenser 40, byproduct condenser 70 andother elements of the processing system in a simple flow diagram. All ofthese remaining elements are shown in FIG. 2 and the operation of theseelements is discussed in greater detail in connection with FIG. 2.Generally, though, the deodorizer will treat the bleached oil to driveoff volatilizable impurities in the oil, yielding a deodorized oil. Thedeodorized oil may be delivered from the deodorizer to an oil storagefacility 28 or a further processing facility (not shown) via an outletline 26 e.

The impurities and other compounds are passed from the deodorizer 20 tothe recovery condenser 40 in a volatiles stream via a vapor conduit 30.The recovery condenser may preferentially condense a glyceride-richrecovered fluid, which may comprise an oil, and pass an impurity-richbyproduct vapor to a byproduct condenser 70 via a byproduct vaporconduit 68. The recovered oil may be delivered to a recovered oilstorage container (not shown in FIG. 1) or, desirably, returned to aprevious stage of the oil processing system. For example, the recoveredoil may be delivered to the degumming/alkali refining subsystem 12 via afirst delivery line 62 a, to the bleaching subsystem 14 via a seconddelivery line 62 b, or back into the deodorizer 20 via a third deliveryline 62 c. In one embodiment of the invention, the recovered oil has animpurity content sufficiently low to justify delivering it to thebleaching system 14 via a second delivery line 62 b rather than goingall the way back to the refining subsystem 12 for further refining.Alternatively, the recovered oil may be delivered to a recovered oilprocessing facility 62 e via a fourth delivery line 62 d.

The impurity-rich byproduct vapor stream delivered through the byproductvapor conduit 68 is condensed in the byproduct condenser 70. This yieldsa byproduct condensate which may be delivered to a byproduct condensatecontainer 88 via a byproduct condensate output line 85. A remainder ofthe byproduct vapor stream, typically consisting primarily of steam,will pass from the byproduct condenser 70 to the vacuum system 90 via anexit conduit 78.

FIG. 2 shows certain components of the system broadly outlined in FIG. 1in more detail. FIG. 2 does not specifically illustrate the bleachingsubsystem 14 or any of the other elements upstream of the bleachingsubsystem 14, however.

As shown in the upper left corner of FIG. 2, bleached oil is deliveredfrom the bleaching subsystem 14 (not shown) to the deodorizer 20 via thebleached oil feed line 15. The deodorizer 20 may be any of a widevariety of commercially available vegetable oil deodorizing systems,such as those sold by Krupp of Hamburg, Germany; De Smet Group, S.A. ofBrussels, Belgium; Gianazza Technology s.r.l. of Legnano, Italy; S.A.Fractionnement Tirtiaux of Fleurus, Belgium; Alfa Laval AB of Lund,Sweden, or others. In the system shown in FIG. 2, the deodorizer 20includes a series of separate deodorizing chambers 22 a-e arranged inseries to treat the bleached oil. Progressively deodorized oil will passfrom one of the deodorizing chambers 22 to the next until the oil issuitably deodorized. Hence, bleached oil will pass through the firstdeodorizer chamber 22 a, then to the second deodorizer chamber 22 b viaa first chamber outlet 26 a. Oil deodorized in the second deodorizerchamber 22 b will be delivered to the third deodorizer chamber 22 c viaa second chamber outlet 26 b. The further deodorized vegetable oil willthen pass through the third chamber outlet 26 c to the fourth deodorizerchamber 22 d and from the fourth chamber 22 d to the fifth chamber 22 evia a fourth chamber outlet 26 d. Vegetable oil in the fifth deodorizerchamber 22 e may be delivered via a fifth chamber outlet 26 e to adeodorized oil storage container 28.

While the deodorizer illustrated in FIG. 2 has five separate deodorizerchambers 22 a-e, it should be understood that any suitable number ofdeodorizer chambers may be employed. In certain embodiments, a singledeodorizer chamber 22 may be employed. This single deodorizer chamber 22may have any number of separate trays. Such a structure is shown in FIG.3 and discussed in more detail below. If so desired, the last deodorizerchamber 22 e may function as a heat exchanger. Bleached oil from thebleaching subsystem 14 may be delivered to the heat exchange chamber 22e via the bleached oil feed line and preheated in heat exchange tubes23. Thereafter, the pre-heated bleached oil can be delivered to thefirst deodorizing chamber 22 a via the bleached oil feed line 15 a.

The deodorizer chambers 22 are desirably maintained at an elevatedtemperature and a reduced pressure to better volatilize thevolatilizable impurities in the vegetable oil. The precise temperatureand pressure may vary depending on the nature and quality of thevegetable oil being processed and the temperature may even vary from oneof the deodorizer chambers 22 to the next. In one embodiment of theinvention, each of the deodorizer chambers is maintained at a pressureof no greater than 10 mm Hg. In one particular embodiment, each of thedeodorizer chambers 22 is maintained at a pressure of no greater than 5mm Hg, e.g., 1-4 mm Hg. The low pressure in the deodorizer chambers 22may be provided by a vacuum system 90. The vacuum system 90 shown inFIG. 2 is not in direct communication with the deodorizer chambers 22.Instead, the vacuum system 90 acts on the deodorizing chambers 22 viavapor conduits 30 a-e, recovery condenser 40, byproduct vapor conduit68, and byproduct condenser 70. A large variety of suitable vacuumsystems are commercially available for use in vegetable oil processing.Most commonly, multi-stage steam jet ejectors will be employed, with athree-stage steam jet ejection system being deemed suitable. If sodesired, an ice condensing system can be included at the inlet end ofthe vacuum system 90 to remove water from the vapor before it isdelivered to such a steam jet ejection system.

The temperature in the deodorizing chambers may be varied as desired tooptimize the yield and quality of the deodorized oil. At highertemperatures, reactions which may degrade the quality of the oil willproceed more quickly. For example, at higher temperatures, cis fattyacids may be converted into trans form. Operating the deodorizer atlower temperatures may minimize the cis-to-trans conversion, but willgenerally take longer to remove the requisite percentage of thevolatilizable impurities in the oil. For most vegetable oils,maintaining the oil at a temperature of 200° C. or higher shouldsuffice. In many circumstances, an oil temperature of about 230-285° C.is suitable, with temperatures of about 240-270° C. being useful formany oils. In one exemplary embodiment useful in physically refiningpalm oil, the first deodorizing chamber 22 a is maintained at a pressureof 2-3 mm Hg and the vegetable oil is heated to a temperature of about260-270° C. Temperatures of about 240-250° C. and pressures of about 1-4mm Hg are appropriate for deodorizing hydrogenated oils andalkali-refined soybean oil, rape oil, and sunflower oil. For physicalrefining of coconut oil or palm kernel oil, temperatures of about240-245° C. and pressures of about 1-4 mm Hg are suitable. Coconut oilwhich has been alkali refined may be deodorized at a lower temperatureof about 200-220° C. at a pressure of about 2-3 mm Hg.

The temperature of the vegetable oil in the deodorizing chambers 22 maybe elevated and controlled in any suitable fashion. In one embodiment,the oil may be heated, at least in part, by a supply of heated steam. Insuch an embodiment, a steam generator 25 may deliver a recirculatingflow of steam through the deodorizer chambers 22 a-e via a series ofsteam delivery lines 25 a-e, respectively. The steam delivery lines 25a-e are closed lines, merely passing heated steam through the chambers22 a-e through closed conduits 27 a-e, respectively.

A quantity of steam, typically from a steam source (not shown) separatefrom the steam supply 25, may be delivered through low-pressure (e.g.,1-5 Bar) steam lines to sparge pipes (not shown) which sparge steamthrough the liquid vegetable oil in the deodorizer chambers 22. As thesteam, which may be superheated, bubbles through the vegetable oil, itwill help strip the volatilizable impurities from the vegetable oil.This produces a steam-containing vapor stream which is delivered fromthe deodorizer to the recovery condenser 40. The vapors from the heatedvegetable oil exiting all of the deodorizer chambers 22 a-e may bedelivered to the recovery condenser 40 through a common vapor conduit30. In the illustrated embodiment, each of the deodorizer chambers 22a-e is provided with a separate vapor conduit 30 a-e, respectively, todeliver vapors directly to the recovery condenser 40. The flow rate ofsteam through the vegetable oil will vary depending on the nature andquality of the oil being deodorized or physically refined and thepressure and temperatures in the deodorizer chambers 22 a-e. Generally,though, steam flow rates on the order of 0.7-2.5 weight percent (wt. %)of the oil flow rates should suffice for most common processingconditions.

As the steam from the steam supply 25 bubbles through the vegetable oil,it may liberate liquid droplets of vegetable oil. These liquid dropletscan be entrained in the flow of vapor from the deodorizer chambers 22 tothe recovery condenser 40. As will be explained below, the recoverycondenser 40 is adapted to help remove these droplets from the vaporstream. Nonetheless, in certain embodiments, the invention employs adeodorizer demister 34 to help remove at least a portion of theentrained droplets from the vapor stream exiting the deodorizer 20. Inthe illustrated embodiment, a single deodorizer demister 34 ispositioned in a dome 32 above the first deodorizer chamber 22 a, butnone of the other deodorizer chambers 22 b-e are provided withdemisters. It should be understood, though, that any desired number ofdemisters may be employed and one demister or multiple demisters may beutilized in connection with each vapor conduit 30 if deemed necessary.

Any known demister construction may be employed. For example, thedeodorizer demister 34 may include one or more knitted wire mesh padswhich span substantially the entire cross-sectional area of the dome 32.Such wire mesh demisters are commercially available. In one embodiment,the deodorizer demister 34 is selected to reduce droplet entrainmentwithout unduly impacting gas flow therethrough. This helps minimize thepressure drop across the demister 34 and enhance efficiency of thedeodorizer 20 without increasing demands on the vacuum system 90.

As explained above, the vapor stream exiting the deodorizer 20 ideallycontains all of the volatilizable impurities in the oil while leavingall of the desirable glycerides and other components in the deodorizer20. In practice, not all of the impurities in the vegetable oil will beremoved and some portion of the desirable components of the vegetableoil will be carried off in the vapor stream. The deodorizer desirablyremoves at least a majority (i.e., greater than 50%) of thevolatilizable impurities in the vegetable oil and, more desirably,removes a substantial fraction of the volatilizable components, leavingnone or only a relatively minor fraction of the volatilizable impuritiesin the deodorized vegetable oil. In the embodiment of FIG. 2, a majorityof the volatilizable impurities which are removed from the vegetable oilwill be removed in the first deodorizing chamber 22 a, with decreasingvolumes of impurities being removed in subsequent deodorizing chambers22 b-e. This can be altered by changing the temperature, residence time,or steam flow rates through each of the deodorizer chambers 22individually.

The vapor stream from the deodorizer 20 may be cooled in the recoverycondenser 40. In the illustrated embodiment, the recovery condenser 40comprises a condensing chamber 42 which is adapted to collect a pool ofrecovered oil 44 adjacent the bottom thereof. Vapor from the vaporconduits 30 is delivered at various heights above the pool 44 and flowsdownwardly toward the pool 44. The vapor then exits the condensingchamber 42 through a byproduct vapor conduit 68 positioned toward thelower end of the condensing chamber 42 but above the pool 44. In analternative embodiment, the vapors are directed upwardly from the vaporconduits 30 and exit the recovery condenser 40 toward the upper end ofthe recovery condenser 40. It is anticipated that such an upward vaporflow may facilitate recovery of the recovered oil.

The vapor conduits 30 a-e may discharge into the condensing chamber 42in any desired direction. In the schematic view of FIG. 2, the firstvapor conduit 30 a is shown as delivering vapor directly downwardlygenerally along a central axis of the condensing chamber 42 while theremaining vapor conduits 30 b-e deliver vapor at an angle downwardlytransverse to that axis. In an alternative embodiment, the flow of vaporfrom the vapor conduit is redirected to increase contact with the wallsof the condensing chamber 42, such as by introducing the vapor from thevapor conduits 30 generally tangentially.

The vapor stream entering the recovery condenser 40 is only partiallycooled to preferentially condense the less volatile desired componentsin the vapor stream, leaving most of the more volatile volatilizableimpurities largely in vapor form. The temperature and quench rate of thevapor in the recovery condenser can be controlled as desired to increaserecovery of the desired components while minimizing the percentage ofthe impurities in the pool of recovered oil 44. In one embodimentsuitable for physically refining palm oil, for example, the temperatureof the vapor stream in the recovery condenser is reduced to atemperature of no greater than 230° C. In one such embodiment, thetemperature varies along the height of the recovery condenser 40, butremains in a range of about 180-230° C. throughout the passage throughthe recovery condenser 40.

If so desired, one or more demisters may be employed in the recoverycondenser to help remove liquid droplets from the vapor stream. In therecovery condenser 40 of FIG. 2, a first demister 46 a is positionedabove the byproduct vapor conduit 68 and may span substantially theentire cross section of the recovery condenser 40. A wire mesh demistersuch as that noted above in connection with the deodorizer demister 34may be employed as the first demister 46 a of the recovery condenser. Asecond demister 46 b may be disposed adjacent the inlet end of thebyproduct vapor conduit 68. This can help minimize the entrainment ofdroplets in the byproduct vapor as it exits the recovery condenser 40.One suitable type of demister 46 b for this application is a so-calledchevron demister, which comprises a plurality of chevron- or V-shapedmetal plates which define a tortuous passageway for passage of vaporsinto the byproduct vapor conduit 68.

Recovered oil may be removed from the pool 44 at the bottom of therecovery condenser 40 and delivered to a recovered oil storage 60 via arecovered oil output line 45. If so desired, the recovered oil may bedelivered from the recovered oil storage container 60 or directly fromthe output line 45 to a recovered oil delivery line 62, such as thelines 62 a-d shown in FIG. 1. A float 47 or other suitable mechanism maybe employed to monitor the level of the recovered oil in the pool 44 foruse in controlling the rate at which the recovered oil is removed fromthe pool.

In the illustrated embodiment, the recovered oil is recirculated fromthe pool 44 back into the condensing chamber 42 to help cool the vaporstream as it passes through the recovery condenser 40. In particular,recovered oil is recirculated back into the recovery condenser via arecovered oil recirculation line 50. A pump 54 may be used to pump therecovered oil through the recovered oil recirculation line and to one ormore spray heads 52. The embodiment of FIG. 2 employs a separate sprayhead 52 a-e for each of the vapor conduits 30 a-e, respectively. Theflow rates of the recovered oil through each of the spray heads 52 a-e,the droplet size of the oil being sprayed, and the angles of the sprayheads 52 a-e with respect to the direction of vapor flow through theconduits 30 a-e may be controlled to better control the profile of thetemperature within the recovery condenser 40 and to achieve the desiredintimacy of contact between the vapor and the oil droplets. The sprayheads 52 may be positioned at any location in fluid communication withthe interior of the condensing chamber 42. In the illustratedembodiment, the spray heads 52 a-e are shown as disposed in the vaporconduits 30 a-e, respectively. It should be understood, though, that oneor more of the spray heads 52 may be positioned beyond the outlet end ofthe respective vapor conduit 30 and spray the recovered oil directlyinto the interior of the recovery condenser. While spraying is employedin one embodiment of the invention, it may be possible to contact thevapor with the oil in other fashions, such as by dripping oil from anumber of divider channels over a structured packing, as shown in FIG. 3and discussed below.

To better control the quench rate and profile of temperature in therecovery condenser, the recirculating recovered oil may be cooled beforeit is delivered through the spray heads 52. In the illustratedembodiment, the recovered oil recirculation line 50 includes a heatexchanger 56 to help cool the recovered oil. If so desired, the heatexchanger 56 may be used to preheat bleached oil being introduced to thedeodorizer 20 with the waste heat from the recovered oil.

The recovered oil produced in the recovery condenser 40 includes asubstantial fraction, preferably greater than 50% and optimallysubstantially higher, of the desirable components in the vapor streamfrom the deodorizer 20. At the same time, the recovered oil desirablyhas a relatively minor fraction of the impurities removed in thedeodorizer 20. As a consequence, the recovery condenser will yield arelatively impurity-poor recovered oil and a relatively impurity-richbyproduct vapor which may be delivered to the byproduct condenser 70. Asnoted above, it is expected that the desirable components of the vaporstream exiting the deodorizer will often include some percentage ofglycerides, sometimes including both diglycerides and triglycerides. Insuch a circumstance, the recovered oil may be relatively glyceride-richwhile the byproduct vapor may be relatively glyceride-poor.

As the relatively glyceride-poor, impurity-rich byproduct vapor streampasses through the byproduct vapor conduit 68 to the byproduct condenser70, additional droplets entrained in the byproduct vapor may coalesce inthe byproduct vapor conduit 68. If so desired, a weir 69 may bepositioned adjacent the outlet end of the byproduct vapor conduit 68 tocollect liquid in the byproduct vapor conduit and allow the liquid toflow back into the pool 44 of recovered oil.

To increase efficiency of the vacuum system 90 and minimize discharge ofpossible environmental impurities, a byproduct condenser 70 may bedisposed between the recovery condenser 40 and the vacuum system 90. Thebyproduct condenser may take any suitable form to remove a desiredamount of the impurities from the byproduct vapor stream before passingit on to the vacuum system 90. In one embodiment, the byproductcondenser 70 comprises a conventional scrubber of the type commerciallyavailable for vegetable oil deodorizers from S.A. FractionnementTirtiaux of Fleurus, Belgium, among others. In the illustratedembodiment, the byproduct condenser 70 includes a byproduct condensingchamber 72 which collects a pool 74 of byproduct condensate in thebottom thereof. This pool 74 may be recirculated via a byproductcondensate circulation line 80. A pump 84 may be used to recirculate thebyproduct condensate and a heat exchanger 86 may be disposed in thebyproduct condensate circulation line 80 to cool the byproductcondensate before it is introduced to the interior of the chamber 72 viaspray head 82. A float 77 may be provided in the byproduct condensingchamber 72 to monitor the level of the pool 74 of byproduct condensate.Excess byproduct condensate can be removed via output line 85 and storedin a byproduct condensate container 88. This condensate may be disposedof or further processed. If so desired, a demister 76, e.g., a wire meshdemister, may be positioned adjacent an inlet of the exit conduit 78leading to the vacuum system 90. This demister will help remove anyliquid droplets in the gas exiting the byproduct condensing chamber.

The byproduct condensate may include any of the desirable components,e.g., glycerides, which are carried over in minor amounts from therecovery condenser 40 to the byproduct condenser 70. The byproductcondensate desirably also includes a substantial fraction, if notsubstantially all, of the impurities removed from the oil in thedeodorizer 20. Water in the byproduct vapor (e.g., from the steamintroduced in the deodorizer 20) may pass through the vacuum system 90and be condensed. If the vacuum system 90 includes an ice condensingsystem, as noted above, the water vapor can be deposited in the icecondensing system.

In one preferred embodiment, a controller 100 may be provided to controloperating parameters of the system shown in FIG. 2. The controller 100may be operatively connected to any number of components, including thesteam supply 25, the pumps 54 and 84, the floats 47 and 87, the heatexchangers 56 and 86, and the vacuum system 90. By monitoringtemperatures, pressures and fluid levels, the controller 100 may be usedto control operation of the deodorizer 20, recovery condenser 40,byproduct condenser 70, and vacuum system 90 to optimize yield andquality of the deodorized oil and the recovered oil within acceptablecommercial operating parameters.

FIG. 3 illustrates an alternative embodiment of the invention. Many ofthe elements in FIG. 3 perform functions similar to like elements inFIG. 2. For purposes of comparison with FIG. 2, therefore, likereference numbers have been used in FIG. 3 to identify functionallysimilar elements, but with the reference numbers in FIG. 3 incrementedby 200. Hence, the deodorizer in FIG. 2 bears reference number 20 whilethe deodorizer in FIG. 3 bears reference number 220.

Whereas the deodorizer 20 of FIG. 2 employs a series of physicallydiscreet deodorizing chambers 22 a-e, the deodorizer 220 of FIG. 3employs a single larger deodorizing chamber with a series of stackeddeodorizing trays 222 a-e. Each of these stacked trays 222 a-e may bethought of as defining effectively separate deodorizing chambers. Suchmultiple-tray deodorizers are well known in the field and arecommercially available from a number of suppliers, including Krupp,DeSmet Group, S.A., and Crown Ironworks of the United States. Such adeodorizer 220 is well suited for physical refining operations. Forexample, the deodorizer 220 may be used in physical refining of coconutoil. In the illustrated embodiment, the second-fifth deodorizing trays222 b-e communicate with a central chimney 229 which directs the vaporsfrom these trays 222 b-e into a second vapor conduit 230 b. The volumeabove the oil level in the first deodorizing tray 222 a is effectivelyisolated from the rest of the deodorizing trays 222 b-e by a centralwall of the chimney 229. A first vapor stream from the first tray 222 amay exit the deodorizer through a dedicated first vapor conduit 230 aand pass into a first recovery condenser 240 a. The first recoverycondenser 240 a may simply comprise a length of an external conduitthrough which the first vapor stream passes, as shown. Alternatively,the first recovery condenser may comprise a domed vessel (similar tothat shown as the second recovery condenser 240 b) or a length ofconduit or a dedicated chamber positioned within the confines of thedeodorizer's outer shell.

The first vapor stream is cooled in the first recovery condenser 240 afrom an elevated initial temperature at which it exits the deodorizer220 to a lower intermediate temperature before it passes into the firstbyproduct vapor conduit 268 a. This will cause a first recovered fluidor “oil” to collect in a pool 244 a in a collection container 243. Thisfirst recovered oil may have very high (over 80%) free fatty acidcontent. As such, it may not be considered a conventional “oil” and maybe alternatively referred to as a first recovered fluid. The vaporstream may be cooled in any suitable fashion. Like the recoverycondenser 40 of FIG. 2, the first vapor stream may be cooled in thefirst recovery condenser 240 a of FIG. 3 by contacting the first vaporstream with the recovered fluid collected in the pool 244 a, e.g., byspraying the recovered fluid via one or more spray nozzles 252 a, bydripping the fluid over a structured packing (not shown) or the like.

The lower intermediate temperature may be selected to preferentiallycondense selected components of the first vapor stream, permitting therest of the first vapor stream to pass into the byproduct condenser 270.The free fatty acids in the bleached vegetable oil are among the firstcomponents to be driven off in the deodorizer 220. The vapor streamgenerated in the first tray 222 a is expected to have a relatively highconcentration of free fatty acids and a lower concentration of otherimpurities in the bleached vegetable oil. By appropriately cooling thefirst vapor stream in the first recovery condenser 240 a, the recoveredfluid collected in the first pool 244 a may have a high percentage offree fatty acids, with free fatty acid percentages in the firstrecovered oil in pool 244 a in excess of 90% being readily obtainablefor at least certain oils. While free fatty acids are not as valuable asthe final processed, deodorized oil, higher-purity free fatty acidsources are useful as a raw material in a number of industrial processesand can command a higher price than conventional deodorizer distillate.

The balance of the vapor stream exiting the deodorizer 220 from trays222 b-e may pass up the chimney 229, through a second vapor conduit 230b, and into a second recovery condenser 240 b. This second recoverycondenser 240 b may include a domed roof and a demister 246 b. Arecirculating flow of a second recovered fluid (which may comprise anoil) from second pool 244 b may be delivered via a second recirculationline 250 b to one or more spray heads 252 b located in the interior ofthe second condensing chamber 242 b. This will cool the second vaporstream from an initial elevated temperature to a lower intermediatetemperature before passing through a second byproduct vapor conduit 268b downwardly to the byproduct condenser 270.

The initial temperature of the second vapor stream may be substantiallythe same as the initial temperature of the first vapor stream as both ofthese vapor streams exit the same deodorizer 220, which may be held at asubstantially constant temperature. In some circumstances, the secondvapor stream may have a different temperature, such as in physicalrefining wherein the second vapor stream will commonly have a lowerpercentage of the free fatty acids and a lower temperature. Theintermediate temperature to which the second recovery condenser 240 bcools the second vapor stream need not be the same as the intermediatetemperature reached at the exit of the first recovery condenser 240 a.To the contrary, the two vapor streams have different compositions andwill yield different recovered fluids in pools 244 a and 244 b.Separately controlling the degree of cooling in the two recoverycondensers 240 a-b enables optimization of each condensation process toenhance yield and/or composition of the recovered fluids.

Hence, two separate vapor streams exit the deodorizer 220 via twoseparate vapor conduits 230 a-b and are selectively cooled in separaterecovery condensers 240 a-b. The byproduct vapor streams exiting therecovery condensers 240 a-b may be treated in separate byproductcondensers. In the illustrated embodiment, however, both of thebyproduct vapor conduits 268 a-b direct their respective vapor streamsinto a common byproduct condenser 270. Construction and operation of thebyproduct condenser 270 may be substantially the same as that of thebyproduct condenser 70 of FIG. 2. In an alternative embodiment, thebyproduct condenser 270 may also include a packing material 283 disposedbetween the byproduct vapor conduits 268 and the spray heads 282 a.Rather than spraying fluid from spray heads 282 a, condensed fluid canbe passed through outlets at the same location and simply drip down ontothe packing material 283. This packing material 283 may further enhancecooling of the byproduct vapor stream and condensation of any impuritiescontained therein. This common byproduct condenser 270 may communicatewith a common vacuum system 290 through an exit conduit 278. Thisenables the deodorizer 220, the first and second recovery condensers 240a-b and the byproduct condenser 270 to be controlled relativelyindependently to yield the desired compositions of the deodorized oil,the first recovered fluid, and the second recovered fluid while sharinga single vacuum system 290.

Methods of Operation

As noted above, certain embodiments of the invention include methods ofprocessing vegetable oil. In the following discussion of theseembodiments, reference is made to the apparatus illustrated in FIGS. 1and 2. It should be understood that this is solely for purposes ofdiscussion and that any suitable apparatus, including but not limited tothat of FIG. 3, could be used instead of the devices shown in FIGS. 1and 2.

One embodiment of the invention provides a method for processing a rawvegetable oil. The raw oil may be introduced to the refining subsystem12 to remove at least some of the free fatty acids, phosphatides andother objectionable components in the oil. If so desired, the raw oilmay be degummed before being subjected to alkali or physical refining,generally as outlined above. The resultant refined vegetable oil may bepassed to the bleaching subsystem 14 via refined oil feed line 13.Refined oil may be bleached in any appropriate fashion. As explainedabove, this may include contacting the refined oil with bleaching clay,activated carbon, or silicates then filtering these bleaching agentsfrom the oil. The bleached oil may be delivered to a suitable deodorizer20 via a bleached oil feed line 15. The refining and bleaching processesmay be carried out on a continuous basis or as batch processes. Ifrefining and/or bleaching are done in a batch process, a batch of oilmay be delivered from the refining subsystem 12 to the bleachingsubsystem 14 and thence to the deodorizer 20.

The parameters of operation of the deodorizer 20 will depend on a numberof factors, including the nature and quality of the oil beingdeodorized, the structure and arrangement of the deodorizer 20, andvarious processing parameters, including residence time in thedeodorizer 20 and the steam flow rates. As explained above, highertemperatures facilitate greater throughput through the deodorizer 20,but can adversely affect the quality of the deodorized oil at longerdeodorizer residence times and can increase the quantity of desirablecomponents in the vapor stream exiting the deodorizer. For mostvegetable oils, a temperature of 200° C. or higher and residence time of30 minutes or more in the deodorizer 20 is necessary to yield acommercially acceptable deodorized oil. In one embodiment useful forpalm oil, for example, an oil temperature of about 230-285° C. and adeodorizer pressure of less than 10 mm Hg is useful, with one exemplaryembodiment employing a temperature of about 260-270° C. and a pressurein the deodorizer 20 of about 2-3 mm Hg.

Vapor driven off in the deodorizer may then be delivered via one or morevapor conduits 30 to the recovery condenser 40. The vapor stream exitingthe deodorizer 20 desirably includes a substantial fraction of thevolitalizable impurities in the vegetable oil delivered to thedeodorizer 20 and a relatively small portion of the more desirablecomponents of the vegetable oil. The nature of the desirable componentsin the vapor stream exiting the deodorizer will vary depending upon anumber of factors, including the nature and quality of the oil beingdeodorized and the operating parameters of the deodorizer. Generally,though, the desirable components in the vapor stream may includetriglycerides, diglycerides, tocopherols, sterols, sterol esters, andtocotrienols. The vapor stream may also include droplets of undeodorizedor partially deodorized vegetable oil entrained therein. The volume ofthese droplets in the vapor stream can be reduced by a deodorizerdemister 34 adjacent the outlet of the deodorizer 20, as explainedabove.

The vapor stream may be cooled in the recovery condenser 40 from aninitial elevated temperature to a lower intermediate temperature. Theinitial temperature may be (but need not be) substantially the same asthe temperature of the vapor stream exiting the deodorizer and may varywith the temperature of the oil in the deodorizer chamber 22. Theinitial elevated temperature may be lower than the temperature at whichthe vapor stream exits the deodorizer due to cooling in the vaporconduit 30, though. In one embodiment, cooling begins in the vaporconduit 30, such as by positioning a recovered fluid spray head 52 inthe conduit 30. As noted above, the vapor stream passing through therecovery condenser 40 may be cooled to a lower intermediate temperaturebefore it exits the recovery condenser. This intermediate temperatureshould be selected to optimize recovery of the desirable components inthe vapor stream while reducing the condensation of impurities in thevapor stream into the recovered oil. This lower intermediate temperaturewill typically be determined on a case-by-case basis for a given type ofoil and range of oil compositions, but it generally may be higher if theinitial elevated temperature is higher.

In one embodiment, the intermediate temperature is on the order of50-90%, desirably about 60-80% and, in certain embodiments, 70-80%, ofthe initial temperature (both stated in degrees Celsius). In anotherembodiment, the intermediate temperature is about 0-90° C. lower thanthe initial temperature, with a temperature differential of about 0-40°C. (desirably 10-40° C.) being useful in many deodorizers and atemperature differential of about 30-90° C. (e.g., 30-60° C. or 40-90°C.) being useful in many physical refining processes. In one specificembodiment suitable for processing palm oil, the vapor stream is cooledin the recovery condenser to a temperature of no less than 170° C.,e.g., 170-240° C., desirably 175-185° C., e.g., 180° C., before beingdelivered to the byproduct condenser 70 via the byproduct vapor conduit68.

The composition of the recovered fluid condensed in the recoverycondenser 40 will vary depending on the composition of the vapor streamdelivered to the recovery condenser 40. In one embodiment, though, therecovered fluid includes a substantial fraction of the desiredcomponents in the vapor stream. As noted above, these desired componentscan include glycerides, tocopherols, sterols, and sterol esters. In oneuseful embodiment of the invention, a substantial fraction of therecovered fluid comprises such desirable components and only arelatively minor fraction of the recovered fluid comprises undesirableimpurities from the vapor stream.

The byproduct condenser 70 may further cool the byproduct vapor from theintermediate temperature to a lower final condensing temperature. Again,this final condensing temperature may be varied as necessary toaccommodate differences in operating pressures, oil composition, andenvironmental requirements of the vapor delivered to the vacuum system90. For some oils, cooling the byproduct vapor to too low of atemperature can cause some of the byproducts to unacceptably solidify.Hence, the byproduct vapor from physical refining of palm oil may becooled in the byproduct condenser 70 to a temperature of about 60-80° C.before it is delivered to the vacuum system 90, while the byproductvapor from most soft seed oils can be cooled to lower temperatures,e.g., 30-50° C.

Certain aspects of the present invention are exemplified in thefollowing examples. These examples are merely illustrative, however, andare not to be construed as limiting the invention in spirit or scope tothe specific procedures or compositions described therein.

Example 1

A bleached, unrefined palm oil was delivered to a deodorizer analogousto the deodorizer 20 schematically illustrated in FIG. 2. The oil ineach of the deodorizer chambers was maintained at a temperature of about270° C. and the pressure in the chambers was about 2-3 mm Hg. The vaporstream was cooled in the recovery condenser 40 to a temperature of about180° C. The recovered fluid from the recovery condenser had a free fattyacid content of about 40 wt. %, with the balance believed to beprimarily glycerides and other desirable components of the raw vegetableoil. This recovered fluid was then returned to the flow of oil enteringthe bleaching subsystem. The byproduct vapor from this process waspassed into the byproduct condenser and cooled further to about 60-80°C. The resultant byproduct condensate was found to contain about 93-95wt. % free fatty acids.

In conventional operation wherein a standard deodorizer is operatedunder the same conditions and all of the vapor stream is passed to astandard Tirtiaux scrubber, the expected free fatty acid content of thedistillate collected in the scrubber was found to be about 85-88 wt. %,substantially less than the 93-95 wt. % found in the byproductcondensate noted above. It is believed that most, if not all, of theincrease in the free fatty acid content achieved in accordance with theinvention can be attributed to the presence of desirable components ofthe vegetable oil in the scrubber distillate in the conventionalprocess. Typical bleached palm oil will have a free fatty acid contentof about 4 wt. %. By rough approximation, this represents a reduced lossof about 0.25% [4*(1/0.88−1/0.93)] to about 0.50% [4*(1/0.85−1/0.95)] ofthe amount of processed oil. Improving yields by one quarter to one halfof a percent represents a very substantial commercial advantage in thehighly competitive vegetable oil market.

Example 2

Bleached, unrefined coconut oil was physically refined in a systemanalogous to that shown in FIG. 3. All of the trays 222 in thedeodorizer were maintained at about 240-245° C. and about 2-3 mm Hg. Thefirst recovered fluid collected in the collector 243 had a free fattyacid content in excess of 80 wt. The second recovered fluid (pool 244 b)had a free fatty acid content of about 30 wt. % and this secondrecovered fluid was returned to the oil supplied to the bleachingsubsystem.

For conventional physical refining of coconut oil using a standarddeodorizer and a standard scrubber, the free fatty acid content of thescrubber distillate will vary significantly depending on the deodorizerconditions. For refined oils having a free fatty acid content of about0.06 wt. %, the free fatty acid content of the standard scrubberdistillate would be expected to be about 60-65 wt. %. For a higherquality refined oil with a free fatty acid content of about 0.02 wt. %,the free fatty acid content of the scrubber distillate can drop to 55wt. % or lower. Again, a significant proportion (if not substantiallyall) of the drop in free fatty acid content of this scrubber distillateis believed to represent desirable components of the oil. As aconsequence, the cost difference between a medium quality oil (0.06 wt.% free fatty acids) and a high quality oil (0.02 wt. % free fatty acids)using conventional processing systems is quite substantial.

The process of the embodiment of the invention outlined above yieldedfree fatty acid contents in the second recovered fluid much higher thanthe free fatty acid content of conventional scrubber distillate (over 80wt. % versus 60-65 wt. %). This can represent a significant commercialadvantage when producing the same quality oil in both processes.

Alternatively, the coconut oil can be refined more heavily to drive offmore of the free fatty acids, polycyclic aromatic hydrocarbon (PAH)constituents, and other undesirable components. This will produce ahigher quality refined oil without significantly dropping yields becausemuch of the additional desirable components driven off with theadditional free fatty acids can be recovered and returned to the oilsupplied to the deodorizer 220. PAH is often removed, in part, bytreating the oil with activated carbon; by refining the oil moreheavily, the activated carbon requirements can be reduced withoutadversely affecting the quality of the final product. Hence, refiningmore heavily can also deliver a significant commercial advantage overconventional processes.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method of processing a partially processed oil including glyceridesand a volatilizable impurity fraction, the method comprising: drivingoff an initial volatiles stream from the partially processed oil, theinitial volatiles stream comprising a portion of the glycerides and atleast a portion of the volatilizable impurity fraction, leaving aprocessed oil; introducing the initial volatiles stream into a firstcondensing chamber; condensing from the initial volatiles stream aglyceride-rich, impurity-poor first condensate, leaving aglyceride-poor, impurity-rich reduced secondary volatiles stream; andpassing the reduced secondary volatiles stream into a second condensingchamber and condensing a glyceride-poor, impurity-rich second condensatefrom the reduced secondary volatiles stream.
 2. The method of claim 1wherein the first condensate contains a minor fraction of thevolatilizable impurities in the initial volatiles stream.
 3. The methodof claim 1 wherein the first condensing chamber is maintained at apressure of no greater than 10 mm Hg.
 4. The method of claim 1 whereinthe first condensing chamber is maintained at a pressure of no greaterthan 5 mm Hg.
 5. The method of claim 1 wherein the initial volatilesstream is driven off by passing steam through the partially processedoil, the initial volatiles stream further comprising steam.
 6. Themethod of claim 1 wherein the partially-processed oil includestocopherols, the initial volatiles stream further comprising a portionof the tocopherols, a majority of the tocopherols in the initialvolatiles stream being condensed in the first condensate.
 7. The methodof claim 1 wherein the first volatiles stream is contacted with thefirst condensate to cool the first volatiles stream.
 8. The method ofclaim 7 wherein the first condensate is sprayed in the first volatilesstream.
 9. A method of processing a triglyceride-containing oil,comprising: bleaching the oil to yield a bleached oil comprisingglycerides and a volatilizable impurity fraction; deodorizing thebleached oil to yield a deodorized oil and a first volatiles stream, thefirst volatiles stream comprising a portion of the glycerides and amajority of the volatilizable impurity fraction; and partiallycondensing the first volatiles stream to yield a glyceride-rich firstcondensate and a glyceride-poor second volatiles stream, the secondvolatiles stream comprising the majority of the volatilizable impurityfraction.
 10. The method of claim 9 further comprising refining the oilprior to bleaching.
 11. The method of claim 9 further comprisingbleaching the first condensate with the oil to yield the bleached oil.12. The method of claim 9 further comprising condensing the secondvolatiles stream to yield a byproduct liquid.
 13. The method of claim 9wherein the first condensate contains a minor fraction of thevolatilizable impurities in the first volatiles stream.
 14. The methodof claim 9 wherein the first volatiles stream is partially condensed bycooling the first volatiles stream from an initial elevated temperatureto a lower intermediate temperature.
 15. The method of claim 14 whereinthe intermediate temperature is between 170° C. and 240° C.
 16. Themethod of claim 9 wherein the first volatiles stream is condensed in afirst condenser maintained at a pressure of no greater than 10 mm Hg.17. The method of claim 9 wherein the first volatiles stream iscondensed in a first condenser maintained at a pressure of no greaterthan 5 mm Hg.
 18. The method of claim 9 wherein the first volatilesstream is condensed in a first condenser and the second volatiles streamis condensed in a second condenser.
 19. The method of claim 18 whereinthe first condenser and the second condenser are each maintained at apressure of less than 5 mm Hg.
 20. The method of claim 18 wherein thefirst volatiles stream is contacted with the first condensate to coolthe first volatiles stream.
 21. The method of claim 20 wherein the firstcondensate is sprayed in the first volatiles stream.
 22. A method ofprocessing a vapor stream from an oil deodorizer, the vapor streamcomprising desirable glycerides and undesirable impurities, comprisingpartially cooling the vapor stream to preferentially condense aglyceride-rich recovered oil, yielding an impurity-rich byproduct vapor.23. The method of claim 22 wherein the vapor stream is contacted withthe recovered oil to cool the vapor stream.
 24. The method of claim 20wherein the recovered oil is sprayed in the first volatiles stream. 25.The method of claim 22 further comprising condensing a byproduct liquidfrom the byproduct vapor.
 26. The method of claim 22 wherein therecovered oil contains a minor fraction of the volatilizable impuritiesin the first volatiles stream.
 27. The method of claim 22 wherein thevapor stream is partially condensed by cooling the vapor stream from aninitial elevated temperature to a lower intermediate temperature. 28.The method of claim 27 wherein the intermediate temperature is between30° C. and 90° C. lower than the initial elevated temperature.
 29. Themethod of claim 22 wherein the vapor stream is condensed in a recoverycondenser maintained at a pressure of no greater than 10 mm Hg.
 30. Themethod of claim 22 wherein the vapor stream is condensed in a recoverycondenser maintained at a pressure of no greater than 5 mm Hg.
 31. Amethod of processing an oil comprising desirable components andvolatilizable impurities, comprising: introducing the oil into a vesselmaintained at a pressure of no greater than 10 mm Hg and contacting theoil with steam in the vessel to volatilize a substantial fraction of theimpurities and a minor fraction of the desirable components into avolatiles stream, leaving a processed oil; passing the volatiles streaminto a recovery condenser maintained at a pressure of no greater than 10mm Hg and partially cooling the volatiles stream to preferentiallycondense a substantial fraction of the desirable compounds into arecovered fluid, leaving a byproduct stream comprising a substantialfraction of the impurities in the volatiles stream, the volatiles streambeing contacted with a portion of the recovered fluid to cool thevolatiles stream; and passing the byproduct stream into a byproductcondenser maintained at a pressure of less than 10 mm Hg and furthercooling the byproduct stream to condense a majority of the remainingimpurities into a byproduct fluid.
 32. The method of claim 31 whereinthe volatiles stream is cooled in the recovery condenser from an initialelevated temperature to a lower intermediate temperature before beingpassed into the byproduct condenser.
 33. The method of claim 32 whereinthe intermediate temperature is between 180° C. and 230° C.
 34. A methodof processing a partially processed oil including glycerides and avolatilizable impurity fraction, the method comprising: driving off afirst volatiles stream from the partially processed oil in a firstdeodorizing segment, the first volatiles stream comprising a portion ofthe glycerides and a first portion of the volatilizable impurityfraction; cooling the first volatiles stream to condense a firstrecovered fluid; driving off a second volatiles stream from thepartially processed oil in a second deodorizing segment, the secondvolatiles stream comprising a portion of the glycerides and a secondportion of the volatilizable impurity fraction, the first and secondportions together comprising a substantial fraction of the volatilizableimpurity fraction; and cooling the second volatiles stream to condense aglyceride-rich, impurity-poor second recovered fluid and leaving aglyceride-poor, impurity-rich byproduct stream.
 35. The method of claim34 wherein the first volatiles stream is cooled by contacting the firstvolatiles stream with a recirculating flow of the first recovered fluid.36. The method of claim 35 further comprising cooling the firstrecovered fluid prior to contacting the first volatiles stream.
 37. Themethod of claim 34 wherein the first volatiles stream is cooled bycontacting the first volatiles stream with a recirculating flow of thefirst recovered fluid and the second volatiles stream is cooled bycontacting the second volatiles stream with a recirculating flow of thesecond recovered fluid.
 38. The method of claim 34 further comprisingpassing the byproduct volatiles stream into a second condensing chamberand condensing a glyceride-poor, impurity-rich byproduct condensate fromthe byproduct volatiles stream.
 39. The method of claim 34 wherein thefirst recovered fluid is collected in a first recovery vessel and thesecond recovered fluid is collected in a separate, second recoveryvessel, the first recovered fluid having a higher percentage of freefatty acids than the second recovered fluid.